1. Field of the Invention
This disclosure generally relates to semiconductor devices and methods of fabricating the same. More specifically, this disclosure relates to semiconductor devices having partially insulated field effect transistors and methods of fabricating the same.
2. Description of the Related Art
As semiconductor devices become highly integrated, a field effect transistor (FET) using a bulk silicon as a body, as is well known, may experience problems such as short channel effects and an increase in the leakage current. FETs that use a substrate having a silicon on insulator (SOI) structure may minimize the above problems but at the cost of increasing the floating body effects such as variance of the transistor threshold voltage or difficulty of heat emission.
The SOI substrate has a structure where an insulation layer and a single-crystal silicon layer are sequentially stacked on a bottom substrate. The floating body effect occurs because the single-crystal silicon layer is insulated and isolated from the bottom substrate. In order to prevent the problems related to the bulk silicon substrate or the SOI substrate, a partially insulated substrate structure has been proposed, in which a predetermined connecting part connects the single-crystal silicon layer to the bottom substrate through the insulation layer.
FIG. 1 is a perspective diagram that illustrates a problem with the conventional method of fabricating a partially insulated substrate using a SOI substrate.
Referring to FIG. 1, a single-crystal silicon layer 3 and an insulation layer 2 are patterned to expose a predetermined region of a bottom substrate 1. Then, an epitaxial silicon layer 4 is formed on the exposed bottom substrate and the single-crystal silicon layer 3.
However, the epitaxial silicon layer 4 is not grown on the insulation layer 2. Thus, according to this method, a void 5 may be formed between the epitaxial silicon layers 4 grown from the bottom substrate 1 and the single-crystal silicon layer 3. The void 5 isolates the single-crystal silicon layer 3 from the bottom substrate 1 to disturb prevention of the floating body effect. Additionally, although the epitaxial silicon layers 4 are grown to contact with each other, since the epitaxial silicon layers 4 are discontinuously connected to each other (refer to a reference number 6), the epitaxial silicon layers 4 are improper for a channel of a transistor.
Embodiments of the invention address these and other disadvantages of the conventional art.